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[Liftoff][arm64] Use wzr/xzr for pushing zero constants

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This is an optimization to avoid an unneeded "mov <reg>, #0"
instruction. Instead, we can just directly use the zero register.

R=ahaas@chromium.org

Bug: chromium:854011, v8:6600
Change-Id: I187d7a659c42d7d4a6d5798eddff8b7ee0983bbc
Reviewed-on: https://chromium-review.googlesource.com/1124684
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54186}
This commit is contained in:
Clemens Hammacher 2018-07-03 17:16:21 +02:00 committed by Commit Bot
parent 720218c2a8
commit 6406b6610c
1 changed files with 11 additions and 19 deletions
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30
src/wasm/baseline/arm64/liftoff-assembler-arm64.h
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@ -957,27 +957,19 @@ void LiftoffStackSlots::Construct() {
asm_->Poke(liftoff::GetRegFromType(slot.src_.reg(), slot.src_.type()),
poke_offset);
break;
case LiftoffAssembler::VarState::KIntConst: {
switch (slot.src_.type()) {
case kWasmI32: {
UseScratchRegisterScope temps(asm_);
Register scratch = temps.AcquireW();
asm_->Mov(scratch, slot.src_.i32_const());
asm_->Poke(scratch, poke_offset);
break;
}
case kWasmI64: {
UseScratchRegisterScope temps(asm_);
Register scratch = temps.AcquireX();
asm_->Mov(scratch, int64_t{slot.src_.i32_const()});
asm_->Poke(scratch, poke_offset);
break;
}
default:
UNREACHABLE();
case LiftoffAssembler::VarState::KIntConst:
DCHECK(slot.src_.type() == kWasmI32 || slot.src_.type() == kWasmI64);
if (slot.src_.i32_const() == 0) {
Register zero_reg = slot.src_.type() == kWasmI32 ? wzr : xzr;
asm_->Poke(zero_reg, poke_offset);
} else {
UseScratchRegisterScope temps(asm_);
Register scratch = slot.src_.type() == kWasmI32 ? temps.AcquireW()
: temps.AcquireX();
asm_->Mov(scratch, int64_t{slot.src_.i32_const()});
asm_->Poke(scratch, poke_offset);
}
break;
}
}
slot_index++;
}